Webs and nonwoven fabrics of chromed collagen fibers

ABSTRACT

Webs or nonwoven fabrics are produced from chromed collagen fiber having mean fiber length of about 1 to 5 cm. which are obtained by chemical or physical treatment of chromed leather. The webs and nonwoven fabrics so produced and articles manufactured therefrom exhibit excellent moisture absorptionrelease performance which is very similar to that of natural leather. Two or more of the thin sheets of the nonwoven fabric so obtained may be laminated to yield products having varying properties. The fabrics may be preferably used as a base for artificial leather particularly for use in making shoes.

United States Patent Inventor Appl. No. Filed Patented Assignees Priority Hiroshi Okamura Tokyo, Japan May 28, 1970 Oct. 26, 1971 Kazunori Wakabayashi Zushi,

Hisao Sato Tokyo; Fuji-Boseki, Kabushiki Kaisha, Tokyo, Japan, part interest to each Mar. 1, 1967 Japan Continuation-impart of application Ser. No. 645,827, June 13, 1967, now abandoned.

WEBS AND NONWOVEN FABRICS 0F CHROME!) COLLAGEN FIBERS 6 Claims, 2 Drawing Figs.

U.S. Cl

16l/DIG.2

[51] Int. 1132b 9/02, B321: 5/26, D04h 1/46 [50] FieldoiSearch 161/154, 153, 156, 169, 226; 162/144, 151; 128/3355 [56] References Cited UNITED STATES PATENTS 1,945,173 1/1934 Woodruff 162/144 3,294,581 12/1966 Hervey et al 162/144 Primary Examiner-Robert F. Burnett Assistant Examiner-Raymond O. Linker, Jr. Attorneys-Robert E. Burns and Emmanuel J. Lobato PATENTEUUEI 26 IS?! FIG. I

RELATIVE HUMIDITY FIG. 2

WEBS AND NONWOVEN FABRICS F CHROMED COLLAGEN FIBERS This is a continuation-in-part of my copending US. application Serial No. 645,827 filed June I3, 1967 now abandoned.

The present invention relates to webs and nonwoven fabrics made wholly of chromed collagen fiber obtained from chromed leather or its blend with other fibers such as cotton, hemp, wool, and the like, natural fibers and/or with synthetic fibers including chemical fibers such as rayon staple fiber.

More particularly, it relates to webs or nonwoven fabrics of chromed collagen or its blend with other fibers, having excel lent moisture absorption-release performance or moisture permeability and entwining ability degrees of which can be intentionally altered to any desired extents.

Many synthetic compositions have been proposed for use as imitation leather, however, all of these suffer from some defect. One of the important characteristics of leather is the property of moisture absorption and release. Other properties which have been difficult to reproduce include desirable tex ture, and handling qualities, resilience, and stretchability.

SUMMARY OF THE INVENTION A principal object of the present invention is the provision of novel, nonwoven fabric having a combination of desirable properties.

Another object of the present invention is the provision of novel, nonwoven fabric which is particularly useful as the base of artificial leather.

A further object of the present invention is to provide an economical process for producing a novel fabric having a combination of desirable characteristics including excellent moisture absorption-release characteristics.

Another object of the present invention is to provide novel webs and nonwoven fabrics having excellent moisture absorption-release properties the degree of which can be easily varied over a wide range depending on the purposes and requirements of the final products made therefrom.

As the result of elaborate study over a long period on the reproduction of moisture absorption-release performance of natural leather, novel web and nonwoven fabrics have been discovered which when made into leather base cloth exhibit very similar characteristics to that of natural leather.

The nonwoven fabric of the invention consists essentially of chromed collagen fibers, which have been separated from chromed leather, having a fiber length of about I to cm. or a mixture of the chromed collagen fiber and at least one other natural or synthetic fiber.

According to the present invention, the webs and nonwoven fabrics are produced from fine fibers of chromed collagen having a length of about I to 5 cm. obtained by chemical or physical treatment of the derm or true skin of natural leather and also by blending the collagen fibers with other fibers.

The articles produced from the nonwoven fabrics of the present invention are especially suitable for use not only as the base of artificial leather, but also as sleeping mats, winter clothes and the like, various packing materials and interior ornamental materials where good moisture absorption-release performance as well as excellent resilience is required. BRIEF SUMMARY OF THE DRAWINGS FIG. 1 is a graph of comparative characteristic of the moisture absorption-release performance of chromed collagen and wool; and

FIG. 2 is an enlarged sectional side view of a nonwoven fabric which was prepared with the use of a web of the present invention. DESCRIPTION OF THE INVENTION Referring to FIG. 1, curve a shows a moisture release performance of chromed collagen and curve b shows the moisture absorption performance of chromed collagen. Further, curve 0 shows the moisture release performance of wool and curve d shows the moisture absorption performance of the wool. In the case of the chromed collagen, the necessary time for the maximum water content of about 60% at the relative humidity of 100% was 24 hours, however, the necessary time for the wool which allowed a maximum water content of about 30% required 192 hours.

As shown in FIG. 1, wool which is considered to have the most excellent moisture absorption-release performance among fibers exhibits a maximum water content of up to about 30% at the relative humidity of 100% and requires a period of as long as 8 days for absorption and release of moisture, whereas the chromed collagen fiber, even though the moisture absorption is about twice as much, needs only one-eighth the time of wool.

This proves the fact that the chromed collagen fiber rapidly takes up and gives off water in an amount more than that of any other fibers and this unique nature constitutes a most desirable property for the practical use of articles made therefrom.

The chromed collagen fiber to be used in the present invention is prepared by a procedure which involves impregnating chromed leather with a sufficient quantity of water so as to loosen the collagen fibrous bundle texture, neutralizing the impregnated leather with dilute alkali solution followed by the addition of sulfate oil to form semidried leather, then beating and opening the resultant dried leather by the use of a fiberopening machine. In this way, fine fibers are formed having a mean diameter of about 0.05 mm. and a length from about I to 5 cm. (It is also possible to obtain fibers having a length greater than 5 cm.) Most of the fibers are about I.5-3.5 cm. long, or more specifically, about 60% of the fibers are about 1.8-2.8 cm. in length. The chromed collagen fiber obtained in this way is different from so called "leather powder" of amorphous type which is prepared by simply grinding chromed leather. In particular, the present fibers have excellent intertwining characteristics and form strong fabrics, even in the absence of a binder.

The present nonwoven fabric is produced by forming a web from the chromed collagen fiber or a mixture of chromed collagen fiber and one or more additional fibers, which are preferably of approximately the same length as the collagen fiber. The web is formed by conventional means such as with a land feeder and/or land webber. The web is then punched to improve the intertwining of the fibers. However, due to the natural high intertwining ability of the present collagen fibers, many fewer needle punchings per sq. cm. are used than are generally required for other fibers and fiber combinations. Usually about 200 punchings per sq. cm. are adequate and up to about 400 punchings per sq. cm. may be used. The fibers are damaged by excessive punchings and preferably punching in an amount of 600 per sq. cm. or more are avoided.

The strands of the chromed collagen fiber are well intertwined with one another or other fibers after the needle punching operation. The high intertwining ability of the present collagen fiber is probably due at least in part to its branched structure. The chromed collagen fiber also swells radially and shrinks lengthwise when soaked in warm water. Thus the present fabric and the intertwining of the fibers may be strengthened further by soaking the fabric in warm water at about 40 C. to C. or C.

The swell shrink phenomenon takes place at about 40 C., but this is not sufficient for an industrial process and non-nal scale of industry. Normally over 60 C. is preferable.

In order to produce practical nonwoven fabrics from synthetic fibers,there has been heretofore no other way than to increase the number of needle punchings and to use binders to consolidate the structure. Such a method has, however, provided some serious disadvantages. The material fiber is injured by a large number of needle punchings, and the binder chokes the gap between fibers, thus providing nonwoven fabrics having little water-absorbing ability and poor handfeeling.

According to the invention, the entwining between collagen fibers or mixture of collagen and other fibers takes place satisfactorily when a chromed fiber of 1-5 cm. length is used as described above, due to the nature of the chromed collagen fiber itself, so that the number of needle punchings required for a satisfactory web is substantially reduced. Further, when any binder is to be used for the purpose of-improving the mechanical strength of the web, the desired effect can be attained with a small quantity of the binder such that the moisture absorption-release performance of the chromed collagen fiber is not substantially changed.

While satisfactory nonwoven fabrics are produced according to the invention in the absence of a binder, conventional binders may be used providing they do not substantially alter nonorientated web by treatment successively with a land feeder and a land webber. Then the web was punched with a fiber rocker to give 200 punchings per square centimeter, soaked in hot water at 7080 C. for about 3 minutes while being held at its both faces with wire gauzes, and passed through mangle rolls to remove water to a satisfactory extent. Then it was dried with a hot air circulation type drier.

The properties of the feltlike shaped material thus produced are as shown in table 1.

TABLE 1 Tetron, (percent) 100 80 70 50 40 20 Chromed collagen fiber (percent) 20 30 40 50 80 Water content (mg./g.) 3. 3 4. 1 7. 0 11. 0 Tensile strength (gJsq. em)- 75*98 120-145 160220 221L298 l71326 Elongation (percent) 45-53 33-45 40 18 44 57 525J Moldability No Poor Good Good Good No 1 Rel. good.

the desirable characteristics and most particularly the moisture absorption-release characteristics of the fabric. Both water soluble and emulsion type binders can be used in the present fabrics. Emulsion type binders include, for example, NBR latex, SBR latex, chloroprene latex, MBR latex, polyacrylic acid ester emulsion, polyvinylacetic acid emulsion, polyvinyl chloride emulsion and the like. Water soluble type binders include, for example, polyvinyl alcohol, polyacrylic acid, and salts thereof, sodium carboxymethyl cellulose, and sodium alginate.

The binder is chosen according to the desired touch of the goods. When a comparatively soft touch is favored, polyacrylic acid ester or NBR latex are suitable, and polychloride viny lidene is useful for a hard touch.

The webs and nonwoven fabrics of the present invention can be widely varied in their strength, elasticity and texture as well as their moisture absorption capacity by varying the proportion of type of fibers mixed with the collagen fibers.

The invention will be illustrated in more detail by the following examples which illustrate the best mode currently contemplated for carrying out the invention but which must not be construed as limiting the invention in any manner. In the examples, all the moisture absorption values are represented by moisture content per gram with respect to the weight of dried fibers based on the weight difference of each fiber when it reaches equibrium at the relative humidity in the range between 65% and 79% at C., and are by weight unless otherwise indicated.

EXAMPLE 1 a. Preparation of the Chromed Collagen Fiber A chromed split is soaked in about 5 parts by volume of a warm aqueous solution containing a nonionic surface active agent at temperature of 50-60 C. for 16 hours and is then washed with water for l hour. The thus treated split is neutralized by tumbling in a rotary drum with about 2 parts by volume of a warm 1% aqueous solution of sodium bicarbonate at a temperature of 40 C. for 1 hour and is subsequently washed with water for minutes. The neutralized split is then oiled by tumbling in a rotary drum with about 2 parts by volume of warm water at 60 C. containing dissolved therein 2.5% by weight, based on the weight of the split, of a sulfated olive oil for 30 minutes; the oiled split is dehydrated by means of a centrifugal separator and dried with hot air at temperatures of at most 50 C. to have a moisture content of about -45%. The dried split is then beaten by means of a stamp mill for 30 minutes, and is disintegrated by pressing it on a scratch roll of a diameter of about 60 cm. having on its peripheral surface a number of saw-toothed flukes and revolving at 1300 rpm.

b. Preparation of a Nonwoven Fabric of Chromed Collagen and Polyethylene Terephthalate A blend of the chromed collagen fiber of 1-5 cm. in fiber length and Tetron (Tetoron: trade name for a polyethylene terephthalate fiber manufactured by Teijin Co., Ltd. and Toyo Rayon Co., Japan) fiber (6 deniers, 3.2 cm.) was formed into As apparent from table 1 the preferred blending ratio of the chromed collagen fiber to obtain webs having the most advantageous combination of characteristics is -60% by Weight. However, a fabric having a higher proportion of collagen fiber or which is made wholly from the present collagen fiber may be used where a very high moisture absorption capacity is desired.

Further the chromed collagen fiber and Tctron fiber were well entwined in spite of the fact that the number of needle punchings is only about one-third to one-fifth that of conventional nonwoven fabric and that the Tetron fiber has no web moldability, and provided nonwoven fabrics having mechanical strengths sufficient for practical use.

EXAMPLE 2 The web was prepared in the same way as in example 1. It was impregnated with a poly(ethyl acrylate) binder emulsion composed of acrylate (solid part 45%) 100 parts, hexamethylol melamine (solid part 80%) 4 parts, organic amine catalyst 0.4 part and water 39.6 parts. The thus impregnated web was squeezed immediately to remove excess emulsion. The resultant sheet was dried first at 120 C. for 15 minutes with an infrared ray, then at 130 C. for additional 20 minutes and then subjected to curing. In this way, the fibers of chromed collagen were intertwined with one another by thermal shrinkage to form a state favorable for manufacturing articles of nonwoven fabrics.

The mechanical properties of the nonwoven fabric thus produced are as shown in table 2.

TABLE 2 Tetron (percent) 60 5O 40 Chromed collagen fiber (percent) 40 60 Tensile strength (kg/mm? 0.61! 0. 72 0.81 Elongation during cutting (percent), 51 58 Tearing strength (kg.lmin.) 0.114 1. 00 1. 24 Bursting strength (kg/em 10.7 11.7 13.4 Rate of humidity absorption (percent) 12 15 Coefficient of adhesion of binder (percent) (against the weight of fibers) 40 40 40 Of the nonwoven fabrics tabulated above, one prepared by blending 40% ofTetron and 60% of chromed collagen has longitudinal-to-transverse ratios of tearing resistance, tensile strength and elongation of 1:1, 0.821 and 07:1, respectively. This means that this nonwoven fabric has no directional difference in strength.

EXAMPLE 3 TABLE 3 Nylon (percent) 100 60 40 20 0 Chromed collagen fiber (percent) 0 20 40 60 80 Moisture absorption (mg./g.). 1. 8 2.60 6.02 9.24 10. ()2 13.14

it will be understood from this result that the blended web consisting of 60% by weight of the chromed collagen fiber and 40% by weight of nylon fiber has a moisture absorption capacity as much as in excess of 5 times that of a web made wholly of nylon fiber.

EXAMPLE 4 TABLE 4 Cotton (percent) 60 40 2O 0 Chromed collagei (pcrc ent) 0 40 6O Moisture absorption (mg./g.) 8.62 9.04. 10.37 11.59 12.04

An example of a laminated nonwoven fabric is shown in FIG. 2 showing an enlarged section of a part of the laminated sheet in which a sheet 1 is made of a thin nonwoven fabric sheet comprising 80% by weight of the chromed collagen fiber and 20% by weight of Tetron fiber and a sheet 2 laminated thereon is made of another thin nonwoven fabric sheet comprising by weight of short cut nylon fiber and 20% by weight of Tetron fiber. An adhesive 3 holds the layers together.

In such laminated nonwoven fabric sheets, it is preferable to use the fiber having the shorter length as the upper layer sheet.

lt may be supposed that the penetration of moisture throughout the laminated sheet would be somewhat impeded by the adhesive layer 3 provided between two sheet layers. However, the moisture absorption of leather is not effected solely by the penetration of moisture through one side to another, but is usually realized by absorption of ambient moisture inside the leather texture until reaching an equilibri' urn condition and release of the absorbed moisture when the condition becomes contrary. Accordingly, the degree of moisture absorption is mainly dependent upon the moisture absorption-release performance of the nonwoven fabric sheet used in the laminate.

In the structure of the nonwoven fabric laminated sheet shown in FIG. 2, the sheet 1 has a moisture absorption as high as nearly 9.0 mg./g. as seen from table 1, so that the artificial leather prepared from the laminated sheet as the base exhibits high water-vapor absorption property which in turn gives pleasant wearing feeling similar to that obtained from natural leather articles, especially shoes since it effectively absorbs perspiration and warmth-keeping property is not reduced.

It is to be noted that the minimum length of the chromed collagen fiber with which it can still entwine with synthetic fibers blended in the present invention is about 1. cm. Chrome collagen fiber which is shorter does not have adequate entwining ability.

Further, according to the present invention, not only different nonwoven fabrics can be manufactured by varying the texture density of the nonwoven fabric and content of binders impregnated as well as the kind and blending ratio of the fiber to be blended, but also nonwoven fabrics having the desired texture and water absorption property can be realized by laminating plural layers of thin nonwoven fabric sheets of the present invention.

Fabrics of the present invention are particularly useful as a base material for synthetic leather for shoes, gloves and other articles wherein the combination of qualities found in natural leather has been found to be especially desirable.

What I claim as new and desire to secure by Letters Patent is:

l. A nonwoven fabric consisting essentially of chromed collagen fibers separated from chromed leather and having a fiber length of about 1 to S cm. or a mixture of said chromed collagen fiber with at least one of other natural or synthetic fibers, said fabric being free of binders, and said collagen fibers being highly entwined and providing a high degree of moisture absorption-release capacity.

2. A fabric according to claim 1 in which said fabric is composed of a mixture of said chromed collagen fiber and at least one fiber selected from at least one member of the group which consists of cotton, hemp, wool, rayon, nylon, and polyethylene terephthalate.

3. A fabric according to claim 1 which contains about 40 to 60% by weight ofsaid chromed collagen fiber.

4. A fabric according to claim 1 containing about 40 to 60% of chromed collagen fiber and remainder being selected from at least one fiber selected from polyethylene terephthalate fiber, nylon fiber, and cotton.

5. A fabric according to claim 1 in which the length of said collagen fibers are principally of the order of 2 to 4 cm.

6. A fabric according to claim 1 comprising a laminate of at least two thin nonwoven fabric sheets which may be the same or different, each of said sheets consisting essentially of said chromed collagen fibers or a mixture of said chromed collagen fiber and at least one other natural or synthetic fiber, and each of said sheets being free of binders. 

2. A fabric according to claim 1 in which said fabric is composed of a mixture of said chromed collagen fiber and at least one fiber selected from at least one member of the group which consists of cotton, hemp, wool, rayon, nylon, and polyethylene terephthalate.
 3. A fabric according to claim 1 which contains about 40 to 60% by weight of said chromed collagen fiber.
 4. A fabric according to claim 1 containing about 40 to 60% of chromed collagen fiber and remainder being selected from at least one fiber selected from polyethylene terephthalate fiber, nylon fiber, and cotton.
 5. A fabric according to claim 1 in which the length of said collagen fibers are principally of the order of 2 to 4 cm.
 6. A fabric according to claim 1 comprising a laminate of at least two thin nonwoven fabric sheets which may be the same or different, each of said sheets consisting essentially of said chromed collagen fibers or a mixture of said chromed collagen fiber and at least one other natural or synthetic fiber, and each of said sheets being free of binders. 